The last few years have seen drones become an increasingly common sight in our skies. Today, they're piloted by a range of users, from amateur enthusiasts and pizza delivery companies to the military.
In Spain, one business wants to use drones to make air cargo more efficient. Singular Aircraft has developed the Flyox I, an unmanned aerial vehicle (UAV) that can undertake a range of tasks, from agricultural work and goods transport to firefighting, surveillance and search and rescue.
Operated remotely, the vehicle can carry 1,850 kilograms of payload and has been designed to be adaptable.
"We have to deal with any type of landing surfaces, that's why it's amphibious (and) we can land on skis on the ice and snow," Luis Carillo, Singular Aircraft's owner, told CNBC's "Sustainable Energy." "We can land on unprepared surfaces and the plane is able to cope with that type of operation."
Air travel is an integral part of modern life, but it comes at an environmental cost. For example, direct emissions from aviation amount to around 3 percent of the European Union's total greenhouse gas emissions, according to the European Commission.
It's within this context that drones offer something different. "We've brought the technology to a point where it opens up some really new possibilities that are exciting," Anne Goodchild, professor of civil and environmental engineering at the University of Washington, said.
"Drones are so lightweight and so energy efficient that they really can compete in terms of… the cost of delivering with other modes."
Goodchild added that there were some "real implementation challenges and airspace management problems, so I see them being implemented first in areas where overland travel is either really dangerous or impossible or really expensive — very remote areas, areas with very poor existing land infrastructure."